L-cysteine's status is entirely a sourcing question. It has historically been produced from keratin sources — duck feathers, hog hair and, in the past, human hair — but fermentation-produced and synthetic L-cysteine are now widely available. The finished label will not tell you which one is in the dough; the supplier's origin statement will, which is why a review requests it in writing.
What it means for each mark
- VeganKeratin-derived E920 is excluded; fermentation-produced or synthetic L-cysteine passes with an origin statement.
- VegetarianFeather- and bristle-derived L-cysteine comes from slaughter streams and is excluded by most vegetarian standards; fermentation-derived material passes.
Where it typically hides
- Commercial breads, buns, bagels and pizza bases (dough conditioner)
- Reaction flavors, including meat-type flavor systems
- Amino acid blends in supplements
What a certification review asks for
- An origin statement for the L-cysteine — keratin, fermentation or synthetic
- The composition of reaction flavors where meat-type notes appear in the flavor system
- Source declarations for amino acids in supplement formulations
Alternatives
- Fermentation-produced L-cysteine
- Synthetic L-cysteine
- Enzyme-based dough conditioners — deactivated yeast and protease systems
Frequently asked questions
Is L-cysteine vegan?
It depends on the source. L-cysteine can be produced from feathers or hair, which is not vegan, or by fermentation and synthesis, which is. A supplier origin statement settles it; the label alone does not.
Which products most often contain L-cysteine?
Mass-produced baked goods: it relaxes dough for machine processing. It appears as L-cysteine or E920 in the ingredient list.